9 6 16 Hominin Origins and Evolutions Part 1 Evidence for the biological evolution of humans consists of fossilized bone genetic histories and other data Geological contexts of fossils and genetics data agree that the last common ancestry between chimpanzees and modern humans existed between 5 8 million years ago Any species considered more closely related to humans than chimps we call hominims Anthropoid and Hominid Beginnings o First mammals appeared ca 200 mya o First primate like mammals appeared ca 65 mya when dinosaurs went extinct and climate grew coolers o Ancestors of monkeys apes and humans the Anthropoids branched off from a prosimian ancestral line ca 50 mya o First ape like primates the hominids appear ca 23 mya at the beginning of the Miocene o Cladogenesis Tree diagram Meaning a branching off MIOCENE APES o Miocene 23 5 mya is the age of the apes o Adaptive radiation involving populations in Africa Europe and Asia o Nearly 30 genera recognized many with no living descendants o Shift in Earth s plates helps account for radiation out of Africa o At 16 mya Africa docked into Eurasia enabling crossovers o Climate was becoming drier opening up African forests o Proconsul genus of African Miocene hominids with mixture of old world monkey traits and ape traits The African Ape Hominin Split Bipedalism o Humans and their hominin ancestors are distinct from hominoids for BIPEDALISM locomotion on two feet o For a hominoid fossil to be classified as a hominin it has to have evidence for bipedalism o Suggestive fossil evidence for bipedalism dates as early as 7 mya sound evidence dates to ca 4 2 mya o The fossil evidence finds support in molecular data which puts African ape hominin split at ca 7 5 mya Anatomy for Bipedalism o Foot Arch Great toe aligns with others o Pelvis Basin shaped Legs to side Leg sockets angled inward o Legs Femurs angled inward Offset facets at knee Knees lock in extended position o Spine S shaped lumbar curve o Skull Foramen magnum faces downward o Human foot has arch and great toe aligned with others o Propulsion in humans from heel along outside of arch across to ball of foot then out through great to o Human hips are short and basin shaped with leg sockets angled inward o Humans knee offsets angle in knee to give us a straight down angle o Even the human skull shows anatomy for bipedalism straight downward orientation of FORAMEN MAGNUM i e opening of spinal cord and other vital parts on skull of humans 2